HealthDay News — Sunny areas of the world have a lower prevalence of attention-deficit/hyperactivity disorder (ADHD), study findings indicate.

“The preventative effect of high solar intensity might be related to an improvement of circadian clock disturbances, which have recently been associated with ADHD,” Martijn Arns, PhD, from Research Institute Brainclinics in Nijmegen, Netherlands, and colleagues reported in Biological Psychiatry.

Noting that worldwide ADHD prevalence varies by region, the researchers examined the association between the prevalence of ADHD and solar intensity, calculating exposure based on kilowatt hours per square meters per day, using data sets from 49 U.S. states and nine other countries.

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Areas with high solar intensity had a lower prevalence of ADHD, even after controlling for factors such as low birth weight and average income, the researchers determined, with solar intensity accounting for 34% to 57% of the variance in ADHD prevalence.

“These findings likely apply to a substantial subgroup of ADHD patients and have major implications in our understanding of the etiology and possibly prevention of ADHD by medical professionals, schools, parents and manufacturers of mobile devices,” the researchers concluded.

There was no association seen between solar intensity and the prevalence of autism spectrum disorders or major depressive disorder.


  1. Arjns M et al. Biological Psychiatry. 2013; 74(8): 585-590.